1. Field
The invention relates generally to wireless communication and, more particularly, to wireless networks, such as local area networks (LANs) and personal area networks (PANs) commonly referred to as piconets.
2. Background
A “piconet” is generally defined as a wireless personal area network that is composed of a group of wireless devices such as an “access terminal,” an “access point” or both such devices in close proximity to one another. A piconet is typically controlled by an access point that assumes the role of a Piconet Coordinator (PNC) that acts as a master terminal that schedules access to the communications medium for the other access terminals in its piconet. Frames are the basic unit of data transport in a piconet, which can include data, acknowledgment, beacon and MAC command frames.
A PNC may also define a superframe structure consisting of multiple frames, with beacons acting as boundaries and providing synchronization to other devices. The IEEE 802.15.3 standard specifies that the PNC sends a beacon to synchronize data exchanges between the PNC and the terminals in the piconet. The beacon signals a start of a superframe and allows each terminal to reset its superframe clock to zero at the beginning of a beacon preamble.
Certain drafts of the IEEE 802.15.3 standard mandate that all PNC capable devices, when operating as PNC, shall transmit common rate beacon in every superframe and that all PNC capable devices shall be able to receive the common rate beacon and command frames. This mechanism is designed to allow PNC capable devices to become aware of existing piconets, which will allow them to join and, more importantly, prevent them from forming independent piconets that may cause interference to devices that are in range of both piconets.
Unfortunately, a PNC capable device within range of some devices of an existing piconet may not be in range of the piconet's PNC. As a result, such a device (which may be referred to as a “hidden node”) may not detect the beacon preventing it from joining the existing piconet. Even more problematic, the hidden node may form an independent piconet and cause interference to devices that are in range of both piconets.